Casting an epoxy piston with an o-ring?

[us sniper]

I am currently building a "T" piston gun, and my design requires a piston with an o-ring. The piston would fit into a piece of 1/2 L copper pipe. I was wondering if anyone had any ideas for a light weight piston, with an o-ring, that could be made without a lathe. Thank you for any tips or ideas.

[john bunsenburner]

JSR is king of epoxy, he once made a how to on how to cast pistons from epoxy in a syringe, its a great way of doing it, another is on MR.C golfball gun on instructables.com, loot at his sig it gives you the link. Really what you do it take a piece of what ever you piston will be in (chamber if barrel seealing, barrel if chamber sealing) and lubricate the inside(butter works pretty well, it just has to stick to the surface). Now you take a piece of neoprene, or any thick rubber and put it under you tube, take a knife and cut around the pipe so the rubber has the same ID as you "mold". Then put the rubber into the end of your piece of pipe(mold) and it should have a snug fit, if it bulges trim it down until it is fairly straight but fits snugly, now fill the mold up HALFWAY with epoxy, let it cure and then take an O-ring that touches the sides of the mold, push it down so it lies on the epoxy and then pour another layer on, not you let the epoxy cure and tap it out of the mold it should now look as follows(from bottom up): Rubber disc,epoxy, O-ring in epoxy, epoxy and tada, you ahve a piston. (this was made in a hurry PM me for details, or ask some one else, there are plenty of people who know how to do it, most are most probably better at it than me)

[jonnyboy]

Here's a tutorial on epoxy casting. I don't believe it covers including o rings but you could either

1.cast about half the piston slide in o ring and continue to cast
2.just chuck the piston in a drill and take a file to it

[Sticky_Tape]

I have something for you the o-ring is casted right into the fiberglass resin and it has a hot glue tip. Yeah Yeah it doesn't seal but it is an absolute perfect fit which makes it have less friction.
EDIT: me being an idiot forgot the link http://www.spudfiles.com/forums/great-1 ... 15980.html